Research on human and animal influenza in Vietnam will provide new information important in the design and implementation of prevention, control, and treatment strategies and policies required to reduce infection, illness and death from influenza in Vietnam and neighboring countries and will assist in the early detection, treatment, control, and containment of influenza viruses having potential for global spread. The proposal comprises 5 subproject studies that address specific announcement aims and objectives: 1) Co-evolution of human and animal Influenza A viruses, Vietnam, including circulating human seasonal strains as well as highly pathogenic animal strains, including avian influenza A/H5N1 viruses, using genomic sequencing, bioinformatics methods on virus isolates from humans and animals throughout Vietnam; 2) Epidemiology of Influenza A/H5N1 in humans, Vietnam: retrospective summary statistical review and univariate analyses of 108 confirmed cases, 2003-2008; 3) Epidemiology of Influenza A/H5N1 in humans, Vietnam: case-control study of risk factors for infection and disease; 4) Burden of influenza-related acute lower respiratory tract infection (ALRTI) in 3 selected district hospitals, Vietnam; 5) Development of improved methods for the diagnosis of influenza in humans in Vietnam, especially the pilot evaluation of a new and improved method for rapid antigenic identification of A/H3,H1,H5 virus subtypes at point-of-care.